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Phantoms in the Brain

Probing the Mysteries of the Human Mind
V. S. Ramachandran

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This was very cool due to the many neurological case studies, and also the clever experiments that he ran on these people. It generally didn't challenge my big picture, but there's a lot of fascinating details about how the brain actually works. He's somewhat interesting because he is what you might say more “humanist” (liberal?) than e.g. Dennet. He thinks Gould has some good points about evolution, he's fascinated by mind-body connections, and feels that many alternative and traditional health practices probably work. He also has a more middle-ground position on evolutionary psychology, feeling that there is definitely something there, but also that many ludicrous just-so-stories have been proposed.

He seems to have been reading too much philosophy, because he seems to believe in Searle and qualia, but his view on qualia are puzzling because he seems to be a physicalist. He seems to follow Searle in thinking “posessing qualia” is similar to “being conscious”. He also asserts in a rhetorical question that free will is necessarily conscious, which is intuitive, but is wrong as I understand free will and consciousness. Perhaps because it's only obvious in hindsight, he kind of misses the boat on directly explaining phantom limbs. The business of remapping is interesting because of what it tells us about the plasticity of brain maps, but in the end it is clear that the reason that you have phantoms is because your sensation of having an arm is only moderately dependent on having one, and depends primarily on the body model in the brain. Also, the fact that people who've never had arms can have phantoms shows that some things are pretty hardwired. It also gives an interesting flavor of brain organization to know that voluntary arm motion, verbal gesticulation and motion for balance while walking are three separate paths. Interestingly, gesticulation is coordinated by the language region, and he speculates that this is likely due to gesticulation preceding language.

The “blindsight” stuff is cool because it gives a sense of how the brain really works, with the separate spatial and object recognition paths. Ramachandran refers to our unconscious visual/spatial/motor ability as “the zombie.” The woman who can put the letter in the slot even though she can't “see” it, but only when the lights are on. What I think is cool about this, is that (at least to me), it that it gives a hint of the computational organization of the brain, with things being perceived and acted on in various ways in parallel, and never “coming together” in a Cartesian theater. The experiment on normal people where there's a size optical illusion, but this only happens on the conscious pathway, and when people go to grab the apparently different-sized objects, then fingers were correctly spaced the exact same size. His examination of the people who deny they are paralyzed is also very interesting for what it shows about the architecture of belief. The business of squirting ice water in the right ear causes them to stop denying for a half hour, then they start denying again, and also how most often when they stop denying they deny they ever denied. He points out that this is somewhat reminiscent of multiple-personality disorder. Note also that in normal people there is often some degree of multiple personas. Depending on the social context you talk and behave in different ways at work, at home, at church, etc. The idea of “different hats”, etc.

In his theory of confabulation, he emphasizes the dynamic of seeking a consistent world view (as an end in itself.) However, he does give a nod to Dennet's and my idea the social need for explanation may be important. I guess I hadn't really considered the value of having a consistent world view. It's an interesting question to what degree there is a discrete propositional belief system living in the reason module. Certainly I remember having thought about and decided about some issues, and can generate this belief, without recalling exactly why I thought that. However, garden variety belief is not nearly this conscious a process.

How does the brain represent belief systems? Clearly there is no global consistency checking of your belief system, because it is easy to believe things that are inconsistent with each other (that you don't yet have a good story of why they are consistent.) Also, the world is too vague for this to be possible.

Note that confirmation bias shows us that belief consistency has something to do with memory. We easily recall stuff that is consistent. Confirmation bias also strongly suggests that what we represent is primarily consistency, not inconsistency. But it seems that we can maintain several different belief networks or different consistency weights between the same facts, corresponding to different social “hats” or MPD personas.

Also there's the evidence from memory studies that people seem to fill in details in consistent (but not necessarily accurate) ways. To some degree it seems that memory is compressed by not bothering to store things that are consistent with our expectations. My sense of how the brain works is that we don't represent belief systems as disjoint consistent networks. Though this would be pleasingly wasteful, and I like the idea that memories are redundantly encoded in different ways, it just seems to me that in the brain “it's all related, man.” Instead, we generate consistent belief systems on the fly as needed.

It comes back to the idea of story. Social contexts can be seen as ongoing stories. We have an ability to work on several stories at the same time, without any requirement for consistency between the stories.

It is hard to think up a good new story on the spot, so we rehearse our stories. Consider the phenomenon of the “snappy come-back” and how you rarely think of it until afterwards.

It was also interesting the experiments he did with the mirror box to get them to deny the apparent paralysis of their good right arm, showing that the denial is not a consequence of neglect, but rather a problem with detecting the discrepancy between their belief and what is actually happening. This was supported by a PET study. I speculate that perhaps discrepancy detection is in general mediated by emotion. In other words, our ability to test our stories against reality arises entirely from intuition and emotion. The main contribution of the conscious/verbal process is coming up with a consistent story, which is a necessary but not sufficient condition.

It's interesting that he has also noticed the considerable validity of Freudian ideas about the unconscious and defense mechanisms. He says that “Freud's most valuable contribution was his discovery that your conscious mind is simply a facade, and that your are completely unaware of 90% of what really goes on in your brain. (A striking example is the zombie in Chapter 4.)” (p. 152)

“The third great scientific revolution, he claimed (modestly), was his own discovery of the unconscious and the corollary notion that the human sense of “being in charge” is illusory. He claimed that everything we do in life is governed by a cauldron of unconscious emotions, drives and motives and that what we call consciousness is just the tip of the iceberg, an elaborate post hoc rationalization of all our actions.” [p. 156, My italics]

This is indeed the “illusion of conscious will” idea, but did Freud really believe that? If so, it isn't generally understood, or is anyway less accepted than a lot of his nonsense. Of course, this is a terribly nonintuitive idea.

books/phantoms_in_brain.txt · Last modified: 2010/05/24 13:52 by ram